Shape effects in the water entry of panels

We consider the water entry of falling two-dimensional rigid panels with low deadrise angles. Through theory and experiment, we examine the influence of panel shape on purely vertical trajectories and assess the effectiveness of the Wagner model, which assumes ideal fluid and imposes severe approximations on the geometric aspects of the problem. Despite these limitations, the model has been surprisingly successful in describing qualitative and approximating quantitative aspects of the pressure during forced water entry of wedges. In the present work, we provide analytical solutions for the free trajectories of a class of surfaces, and compare with tabletop-scale experiments with several drop heights. One of the more interesting testable predictions is that surfaces whose profile curves upwards more strongly than a parabola will continue to accelerate, while profiles of weaker power will decelerate.